Hazelnuts contain nearly 91 percent monounsaturated fat and less than 4 percent saturated fat. Over 30 tree nut studies indicate this high level of monounsaturated fat is likely responsible for a reduction in both total blood and LDL cholesterol levels when hazelnuts are consumed as part of a low saturated fat diet.

Hazelnuts contain a high concentration of vitamin E which prevents oxidation of the polyunsaturated fats, and it is also one of the few nuts which contain vitamin A, which is a natural antioxidant and has cancer-preventing properties.

The B-group vitamins are also well represented in hazelnuts, particularly vitamin B5 and B6. Moreover, hazelnuts are an excellent source of minerals, particularly the minerals manganese, selenium and zinc, but the protein composition is such that combinations with other nuts, grains or legumes are required in order to obtain the maximum benefit.